@Riot Silvers can't play with Platinums, so why should unranked?

I just had a game where our Voli took heal and tp. He rushed trinity force and he had no keystone. At first I thought he was trolling but then I realized he must have actually been new to ranked. I don't think it's fair that someone can duo with him and have him in a Platinum ranked game and yet you couldn't even invite a Silver, WHICH WOULD DO BETTER THAN THE UNRANKED. I think if you're unranked the highest rank you can play with is Silver AT THE MOST. Even then most people who start playing ranked (actual new players) don't do that well. I'm just mind blown that it's even allowed.